The Avar Khaganate was a highly powerful nomadic empire established by the Pannonian Avars in Central Europe. At its height, it controlled much of the Pannonian Basin and launched devastating raids against the Byzantine Empire, often allying with other groups like the Sasanians or Slavs. The Avars were absolute masters of horsemanship and are widely credited with introducing the iron stirrup to Europe, a revolutionary technology that changed cavalry warfare. With their formidable mounted warriors, they dominated Eastern Europe for centuries and extracted massive tributes from Byzantium. However, their crushing defeat at the Siege of Constantinople in 626 shattered their aura of invincibility, sparking rebellions among their subject tribes. The empire steadily declined until it was finally destroyed by the Frankish king Charlemagne at the end of the 8th century.